The present invention relates to a gas generator particularly suitably used for expanding and inflating a side airbag for side collision or a passenger-side airbag.
One typical example of the heretofore-proposed gas generator to expand and inflate a side airbag or a passenger-side airbag is shown in FIG. 5.
The gas generator of FIG. 5 is designed mainly for expanding and inflating a side airbag. It has an elongated cylindrical housing 51. The housing 51 has in its interior a combustion chamber 52 and a cooling-and-filtering chamber 53 into which the housing 51 is partitioned by a partition ring plate 54 along an axial direction of the housing 51. The combustion chamber 52 is packed with gas generating agents 55 that generate high temperature gas by burning. The cooling-and-filtering chamber 53 fits therein a cylindrical filtering member 56 for filtering and cooling the high temperature gas generated by the burning of the gas generating agents 55. Also, the housing 51 is provided, at an axial end thereof, with an igniter 57 for spurting flame into the combustion chamber 52.
In this gas generator, the igniter 57 is ignited by the application of power thereto under control of collision detection signals from a collision sensor and then the ignition flame is spurted into the combustion chamber 52 to force the gas generating agents 55 to be ignited and burnt, to thereby generate a large quantity of high temperature gas rapidly.
The high temperature gas generated in the combustion chamber 52 passes into the partition ring plate 54 and flows out into the inside of the filtering member 56 fitted in the cooling-and-filtering chamber 53. Then, it flows into the filtering member 56, for slag collection and cooling of the gas thereat and then flows out from gas discharging holes 51a of the housing 51 into the airbag. The airbag is then expanded and inflated rapidly by the large quantity of clean gas discharged from the gas discharging holes 51a. 
In recent years, in the technical field of gas generator, reduction in size and weight of gas generator is being increasingly demanded. When viewed in this light, since the conventional gas generator forming therein the combustion chamber 52 and the cooling-and-filtering chamber 53 has a wasted space in that nothing is filled in the bore of the filtering member 56, there is a given limit in providing reduced size and weight by effectively utilizing the total volume of the housing.
In other words, in the conventional gas generator, when the housing 51 is reduced in diameter to meet the demand for reduction in size and weight, an axial length of the combustion chamber 52 of the housing 51 must be increased to ensure a necessary quantity of gas generating agents 55 packed to expand and inflate the airbag. On the other hand, when the housing 51 is reduced in its axial length, the housing 51 must be increased in diameter, for the same reason.
Also, the conventional gas generator adopts the mode that regardless of the patterns of automobile collision (low-speed collision, high-speed collision, etc.), a large quantity of gas is always discharged to inflate and expand the airbag rapidly. Consequently, the conventional gas generator cannot meet the soft inflation technology capable of providing a controlled expansion and inflation of the airbag in correspondence with the patterns of the automobile collision.
The present invention aims to provide a gas generator that can achieve reduction in size and weight by effectively utilizing the total volume of the housing, while the slag collection and the cooling of the high temperature gas can be ensured by the overall filtering member, and also can provide a controlled expansion and inflation of the airbag.
A gas generator of the present invention comprises an elongated cylindrical housing. The housing has, in its interior, a first combustion chamber, a third combustion chamber formed in a filtering member and a second combustion chamber which are continuously formed in this order along an axial direction of the housing. The combustion chambers are each packed with gas generating agents, and ignition means for igniting the gas generating agents is disposed in at least either of the first combustion chamber and the second combustion chamber.
With this construction, since the gas generating agents are packed in the third combustion chamber formed in the filtering member as well, the total volume of the housing can be effectively utilized for fitting the filtering member in and filling the gas generating agents in the housing. Hence, even if the housing is reduced in diameter, for example, in order to reduce the size and weight of the gas generator, a quantity of gas generating agents packed enough to expand and inflate the airbag can be ensured without increasing the axial length of the housing.
According to the gas generator of the present invention, when the ignition means is ignited by the application of power thereto, the flame is spurted into the first combustion chamber, for example. Then, the combustion runs through the housing in the order of the first combustion chamber, the third combustion chamber formed in the filtering member and the second combustion chamber. The gas generated by the burning of the gas generating agents runs sequentially from the first combustion chamber side to the second combustion chamber side through the third combustion chamber formed in the filtering member. This can allow the high temperature gas to flow into the entire filtering member.
When viewing from this, the gas generating agents packed in the third combustion chamber has the gas generating function of expanding and inflating the airbag and the flame transferring function of transferring the flame and heat generated in the first combustion chamber to the second combustion chamber.
Further, according to the gas generator of the present invention, the gas generating agents packed are made to burn in the order of the first combustion chamber, the third combustion chamber and the second combustion chamber so that the high temperature gas generated in the housing can be controlled in such a manner that a small quantity of gas can be generated, for example, in the first combustion chamber in the initial stage of combustion and thereafter a large quantity of gas can be generated in the respective combustion chambers. The ignition means may be disposed in each of the first combustion chamber and the second combustion chamber and the respective ignition means may be ignited by the application of power thereto with time difference so that the quantity of high temperature gas generated in the housing can be controlled. This enables the gas generator to meet the soft inflation technology capable of providing a controlled expansion and inflation of the airbag.
In the gas generator of the present invention, a variant structure wherein any of the first to third combustion chambers, e.g. the third combustion chamber formed in the filtering member, is packed with no gas generating agents may be adopted.
In the gas generator of the present invention, the gas generating agents in the respective combustion chambers are packed in series.
This enables the gas generating agents packed in the respective combustion chambers to be ignited and burnt continuously by igniting at least either of the gas generating agents packed in the first combustion chamber and those packed in the second combustion chamber.
In the gas generator of the present invention, the ignition means is formed by a single igniter to be ignited by the application of power thereto.
This can provide a simplified structure with no flame transfer agents for transferring the flame of the ignition means and the like arranged in the axial direction of the housing.
For example, in order for the gas generating agents in the first combustion chamber to be ignited by only the flame of the igniter, the flame, the heat and the like spurted from the igniter must be shut up in the first combustion chamber. In the gas generator of the present invention, the respective combustion chambers are formed in series along the axial direction of the housing 1 and also the third combustion chamber is formed to have a smaller diameter than the first combustion chamber and the second combustion chamber, whereby the flame and the heat are easily shut up in the first combustion chamber.
In the gas generator of the present invention, the gas generating agents packed in the first combustion chamber are made different in quantity from the gas generating agents packed in the second combustion chamber.
This enables a quantity of high temperature gas generated in the first combustion chamber and the second combustion chamber to be adjusted.
The quantity of high temperature gas generated can be adjusted by properly changing a volume ratio between the first combustion chamber and the second combustion chamber and adjusting a quantity of gas generating agents packed. Specifically, the volume ratio between the first combustion chamber and the second combustion chamber can be changed by changing the length of the filtering member or changing the position of the filtering member with respect to the housing.
In the gas generator of the present invention, the first combustion chamber is made different in volume from the second combustion chamber.
This enables a quantity of gas generating agents packed in the first combustion chamber and the second combustion chamber to be adjusted. Additionally, a quantity of high temperature gas generated can also be adjusted by adjusting the quantity of gas generating agents packed.
The volume of the first combustion chamber and the volume of the second combustion chamber can be adjusted by changing the length of the filtering member or changing the position of the filtering member with respect to the housing.
In the gas generator of the present invention, a partition member is provided at an end surface of the filtering member.
This enables the high temperature gas generated in the first combustion chamber or the second combustion chamber to be led to the third combustion chamber formed in the filtering member, without flowing out directly into the end surface of the filtering member or the respective gas discharging holes. This enables the flame and the like spurted from the ignition means to be shut up in the first combustion chamber or the second combustion chamber, and as such can allow the flame and the like from the ignition means to be effectively utilized to burn the gas generating agents easily and rapidly.
The gas generator of the present invention fits for a side airbag for side collision.
The side airbag and the like is generally built in vary limited space of an automobile. In view of this, the gas generator of the present invention can meet the demand for reduction in size and weight and is optimum for expansion and inflation of the side airbag.